Founders can be recruited for some time after the application is approved. They do have to be identified, although not sure of the process. The family in question could have been added as a founding family after the application then applied when their children were eligible. Agree with others if you're interested, contact the principal.
+1
Assuming this rumor is even true, I don't see anything improper going on. Adding founders after the application is approved is not unusual. Take a look at the DC Scholars charter application and it says the same thing about recruiting more members to the Founding Group.
People are freaking out about founders being added, but it makes total sense to me that approved schools would need a ton of help between the application process and actually getting the school up and running. It seems that the PCSB recognizes this as well which is why they allow members to be added to the founding group, but it's also a good thing that the PCSB puts a cap on the number of students that can be given preference this way.